using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;


class Magatro
{
    static void Main()
    {
        int min = 1;
        int max = 1000000000;
        while (true)
        {
            int aida = (min + max) / 2;
            Console.WriteLine("? {0}", aida);
            string ans = Console.ReadLine();
            if (ans == "0")
            {
                min = aida+1;
            }
            else
            {
                max = aida;
            }
            if (min == max)
            {
                Console.WriteLine("! {0}",min);
                return;
            }
        }
    }
}